1. Field of the Invention
This invention relates to a controller for a ropeless elevator using a linear motor and, in particular, to a controller which utilizes inductive radio to transmit the position, speed, etc. of the car to a control circuit on the building side, thereby controlling the linear motor.
2. Description of the Related Art
FIG. 4 schematically shows a conventional elevator system. In the drawing, numeral 1 indicates an elevator hoisting machine; numeral 2 indicates a deflector wheel for shifting the elevator rope position; numeral 3 indicates a car/counterweight suspending rope; numeral 4 indicates a car rail for guiding an elevator car 5; and numeral 6 indicates a couterweight rail for guiding a counter weight 7.
This conventional elevator system, constructed as described above, requires the rope 3 for suspending the car 5, so that the system is suitable for a skyscraper having a height, for example, of 1000 m or more, due to the weight of the rope, etc. As a means for solving this problem in the conventional elevator system, a ropeless elevator driven by a linear motor has been disclosed, for example, in Japanese Patent Laid-Open No. 3-23171.
FIG. 5 shows the construction of a ropeless elevator as disclosed in the above-mentioned laid-open publication. In the drawing, numeral 5 indicates an elevator car; numeral 8 indicates a linear motor field formed by a permanent magnet, superconductive coil or the like; numeral 9 indicates linear-motor armature coils provided on the building side; and numeral 10 indicates armature yokes. The armature coils 9 and the yokes 10 are arranged on either side of the elevator so as to guide the elevator car 5 along an elevator hoistway 11. Numeral 12 indicates a guide rail for supporting the elevator, and numeral 13 indicates an upper buffer.
FIG. 6 shows the principle of a ground-primary-type linear motor, which is used in the elevator shown in FIG. 5. Referring to FIG. 6, when three-phase alternating currents are passed through the armature coils 9, arranged on the building side to face the linear motor field 8 on the elevator-car side, in such a way as to generate a progressive magnetic field 8A having a polarity attracting the field and corresponding to the load, a thrust B.L.I (B: magnetic flux density; L: current-side length; I: current), as is clarified in electromagnetics.
FIG. 7 shows a feed control block diagram for the above armature coils 9. The armature coils 9 of FIG. 5 are shown as consisting of armature coils 91L through 94L and 91R through 94R, of which the armature coils 91L, 92L, 93L and 94L are arranged on the left-hand side, and the armature coils 91R, 92R, 93R and 94R are arranged on the right-hand side. The armature coils 91L, 91R, 93L and 93R are fed by an inverter 14a through change-over switches 21 and 23 so as to be excited. The armature coils 92L, 92R, 94L and 94R are fed by an inverter 14b through change-over switches 22 and 24 so as to be excited.
When the elevator car 5 is at a position where it faces the armature coils 91L and 91R, the change-over switch 21 is closed, so that the armature coils 91L and 91R are excited by the inverter 14a. The elevator is driven by the interaction of the current in the excited armature coils and the field 8 attached to the elevator car 5. When the elevator car 5 descends from the position of the armature coils 91L and 91R to that of the armature coils 92L and 92R, the armature coils 91L and 91R are excited by the inverter 14a, and the armature coils 92L and 92R are excited by the inverter 14b. In this process, the change-over switches 21 and 22 are both in the closed position.
When the elevator car 5 has completely moved to the position of the armature coils 92L and 92R, only the change-over switch 22 is in the closed position to excite the armature coils 92L and 92R. Similarly, as the elevator car moves on, the change-over switch 23 is closed to excite the armature coils 93L and 93R, and then the change-over switch 24 is closed to excite the armature coils 94L and 94R. In this way, the elevator car is caused to descend. When causing the elevator car to ascend, the armature coils 9 are successively excited by a sequence reverse to the above-described one.
A control system for a ropeless elevator of the above-described type, in which the elevator car 5 is caused to move by successive excitation of the armature coils 9 provided on the building side, has not been generally established yet. In a linear motor car, which is propelled by the same principle as described above, the position and speed of the car are detected by utilizing cross induction lines because of the high speed of the car. An elevator control system using this method will be described with reference to FIGS. 8 and 9.
Referring to FIG. 8, numeral 40 indicates a cross induction line cable provided in the hoistway of the elevator. The cable includes position detecting line pairs (G1-A, G1-B, G2, , Gn) 41.about.44, data transmission line pairs (D1, D2) 45, 46, and a signal level reference line pair (C) 47. Numerals 57 and 84 respectively indicate an induction radio antenna and an oscillator which are mounted on the elevator car 5.
In the construction shown in FIG. 8, the induction radio antenna 57, mounted on the elevator car 5, is excited by the oscillator 84, thereby inducing an electromotive force in each induction line in the cross induction line cable 40 provided in the elevator hoistway, which faces the antenna 57. As illustrated in FIG. 9, this electromotive force has a pseudo-sinusoidal wave in which the electric potential where the induction lines intersect each other is 0 V.
Accordingly, the induction lines (G1-A and G1-B) 41 and 42 of FIG. 8 are arranged with their intersections 90 degrees offset from each other, as shown in the drawing, so that, as shown in FIG. 9, the electromotive forces induced in the induction lines (G1-A) 41 and (G1-B) 42 are 90 degrees out of phase with respect to each other. Generally speaking, to increase noise margin, 1/0 judgment is made through checking with reference to the sign of the signal level reference pair 47.
The cross induction line cable 40 generally contains a plurality of induction lines 41.about.44 having predetermined codes so as to effect detection of absolute positions, and the accuracy in the detection of position and speed is enhanced through interpolation of the analog values of the pseudo sinusoidal waves of the induction lines. The speed detection has been effected through calculation from positional variation in a predetermined time.
Further, by utilizing induction radio, it is possible to effect variation in positional detection and carrier frequency, thereby making it possible to perform ordinary data communication; by means of the induction lines for data communication (D1) 46 and (D2) 45, communication between the movable body and the ground has been conducted. Since communication is impossible at intersections, two induction lines having their intersections 90 degrees offset, are usually used, as in the case of the communication lines (D1) 46 and (D2) 45.
However, the above-described conventional system for detecting the position and speed of the movable body, which utilizes induction radio, solely utilizes cross induction lines, so that the accuracy in position and speed is determined by the intersection lengths of the cross induction lines. Thus, generally speaking, there is a limit to the enhancement of the minimum detection accuracy even when the analog values of the pseudo-sinusoidal waves of the induction lines are interpolated. Thus, although this system has not involved any problems in the case of railroads, travelling cranes, etc., which have a very large inertia, it has been unsatisfactory in terms of accuracy for uses where the inertia is relatively low and where vibrations, etc. constitute a problem, as in the case of an elevator.